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EXPERIMENT: EFFECTS OF TEMPERATURE ON ENZYMES.
DUE: _____________
CP
AIM: To investigate the effects of temperature on the enzyme catalase.
THEORY: Hydrogen peroxide is a harmful by-product of many normal metabolic processes: To prevent damage, it
must be quickly converted into other, less dangerous substances. To this end, catalase is frequently used by cells
to rapidly catalyse the decomposition of hydrogen peroxide into less reactive gaseous oxygen and water
molecules. Catalase works at an optimum temperature of 37 °C, which is approximately the temperature of the
human body. All animals use catalase in every organ, with particularly high concentrations occurring in the liver.
Potatoes offer another source of the enzyme catalse which is what we will be using.
The reaction of catalase in the decomposition of hydrogen peroxide is: 2 H2O2 → 2 H2O + O2. It is an exothermic
reaction.
HYPOTHESIS: ( Can you test this?)
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EQUIPMENT: Include a list of equipment:
METHOD:
1. Use a cork borer to obtain 2cm lengths of potato, being careful not to cut yourself. The cork borer
increases the accuracy the enzyme quantity and is a controlled variable.
2. Each person is to prepare and maintain a water bath at a particular temperature as listed in the Result
table. Ensure precaution around the hot water.
3. Collect 2 clean test tubes and label A and B. Add 5ml of hydrogen peroxide (substrate) to each test tube.
Place these test tubes in the water bath to come to temperature. Maintain this temperature.
4. Add the prepared lengths of catalase to each test tube. This ensures reliability since the one temperature
is being tested 2 times.
5. Record the height of the bubbles (bottom to top) to the nearest millimetre produced after 2 minutes using
a stop watch to increase accuracy. Comment on the activity in the test tube.
Draw a neat labelled diagram below o accompany the METHOD:
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RESULTS:
Enzyme activity at varying temperatures after 2 minutes:
Temperature (0C)
Height of bubbles in
Height of bubbles in
Average height
Test tube A (mm)
Test tube B (mm)
(mm)
0
10
20
35
45
60
Graph the classes average heights for each temperature.
Comment on activity
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DISCUSSION:
On your own paper by referring to the questions that follow. Incorporate these points into your discussion – do not
just answer them. This is typical of a thorough DISCUSSION and will be expected through out HSC Biology
course. Refer to Experiments and Investigations sheet.
Questions:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Name the dependent variables.
Name the independent variables.
Name the controls.
What did you do to ensure the accuracy of this experiment?
How did you ensure the reliability of this experiment?
Is the experiment valid? Why?
What are some errors of this experiment?
How could you improve this experiment?
Discuss the safety precautions or risks in the experiment. (identify the risk, what harm can it do, how minimise risk)
What caused the hydrogen peroxide to bubble?
What was the optimum temperature for this particular enzyme. Discuss its significance.
Discuss the results of the other temperatures.
Is the graph you constructed expected and typical for enzyme activity?
Discuss how this experiment relates to the objectives.
CONCLUSION:
On your own paper.
USING EXCEL TO PLOT A GRAPH:
NB These instructions will vary
depending on the Windows you are
using.
1.
2.
3.
4.
5.
6.
7.
8.
Highlight and copy table of
values
Open Excel and paste the table
anywhere.
Highlight the table by clicking
and dragging across it.
Then click on “Insert” “Chart”.
Pick a chart type (usually XY scatter) and a sub chart type
“Next” and continue following the prompts.
“Finish”. You can edit the graph in “Sheet” mode if required by double clicking on e.g. labels
Can now copy and paste to a Word Document if required.
Time
Temp
2
4
6
8
10
12
14
11
23
34
45
67
79
89